1. Field of the Invention
This invention relates to a device for sensing feeding of copying papers, which is able to promptly detect jamming and misfeeding of the papers being fed along a copying paper feed route in a copying apparatus, such as a copier or a printer utilizing an electrophotographic system.
2. Description of the Prior Art
Generally, a copying paper feed route of a conventional copying apparatus comprises, as shown in FIG. 1 of the accompanying drawings, a pair of feed rollers 2 through which papers contained in a paper supply tray 1 are fed one by one toward a photosensitive drum 3 where copying is performed thereon, and a pair of discharge rollers 4 for discharging the paper undergone copying operation at the photosensitive drum 3 to paper collection tray 5.
In order to sense possible jamming or misfeeding of the copying paper being fed along the feed route, the prior copying apparatus is provided with sensing devices indicated by "S" in FIG. 1, which are disposed one at each of positions between the paper supply tray 1 and the feed rollers 2, and between the discharge rollers 4 and the paper collection tray 5.
Various sensing devices which are somewhat different in construction from each other depending upon systems have been employed, a typical example of which comprises, as shown in FIG. 2, a photosensor 6 having an ON-OFF function and fixedly secured at one side to a support plate 7, and a generally L-shaped actuate 8 acting to autuate the photosensor 6 and pivotally disposed above the copying paper feed route to detect a paper feeding condition.
With the device thus constructed, when there is no paper (being fed in the direction of "A" in FIG. 2) on the paper feed path, the actuator 8 falls by own gravity into an opening formed in the feed path, thereby getting out of intervention in a slot portion 6a of the photosensor 6, as shown in FIG. 2.
As a result, the photosensor 6 keeps an ON condition indicating the absence of the paper. In this state, when the paper is fed, the actuator 8 held in the descended position is rotated in the direction of the arrow in FIG. 2 by the paper being fed, to be inserted into the slot portion 6a of the photosensor 6, thereby changing the ON condition of the photosensor into the OFF condition which indicates the feeding of the paper.
As described above, the prior art device has the construction in which the photosensor switched on and off by the actuator pivotally movable upward and downward depending upon the feeding condition of the paper simply senses only such a feeding condition of the paper, that is, whether or not the paper passes by the actuator. Therefore, the sensing of abnormality such as a paper jamming phenomenon which may occur at the paper feed path extending from the feed rollers through the photosensitive drum to the discharge rollers is carried out by a pair of the photosensors each disposed in the vicinity of each of the paper supply and collection trays, as shown in FIG. 1, to check paper traveling time at a section between them, so that when discharging of the fed paper is delayed over any given time, the occurrence of the paper jamming phenomenon is detected.
However, according to the prior art, the copying apparatus continues its normal operation for any period of time for sensing a jamming phenomenon by the photosensors and then stopping the operation of the apparatus. Therefore, in case that the jamming phenomenon occurs between the feed rollers and the photosensitive drum, the copying apparatus continues its operation without the paper fed to the photosensitive drum, so that toner may pollute a photosensitive portion and the jammed paper may impart compulsive force to the apparatus. Therefore, copying performance may be lowered and a life of the apparatus may be decreased.